1-aminoanthraquinone is a key ingredient in the manufacture of a large number of dyestuffs, particularly vat dyestuffs. According to prior art teachings, it is desirable to obtain the 1-aminoanthraquinone in as pure a state as possible, since the isomeric aminoanthraquinones and diaminoanthraquinones are regarded as undesirable impurities having an adverse effect on the quality of dyestuffs containing any appreciable amount thereof. The desirability of obtaining pure 1-aminoanthraquinone and the difficulty involved in the preparation of this compound in substantially pure form are illustrated in U.S. Pat. Nos. 2,874,168 and 2,302,729. That a technically satisfactory method of preparing mononitroanthraquinone was not available as of 1949 can be seen from "Fundamental Processes of Dye Chemistry" by Fierz-David and Blangley, Interscience Pub. 1949, at pages 57 and 58.
One synthetic route for making high quality 1-aminoanthraquinone is to sulfonate anthraquinone in the presence of mercury catalyst to obtain the anthraquinone-1-sulphonate and thereafter replace the sulfo group by an amino group by reacting the anthraquinone-1-sulphonate with ammonium hydroxide in the presence of nitrobenzenesulphonic acid at elevated temperatures. The product is of acceptable quality but the mercury catalyst presents the problem of disposing of a mercury-contaminated reaction medium, which disposal problem is attended by rather serious ecological considerations. Thus, one desirous of preparing 1-aminoanthraquinones is faced with two horns of a dilemma. In order to obtain good quality 1-aminoanthraquinones, it is necessary to use a route that results in an unacceptable environmental impact. On the other hand, one desirous of avoiding the use of catalytic mercury, who therefore attempts a different route, is confronted by the general teaching of the literature that direct nitration is an unsatisfactory method. In fact, the nitration of anthraquinone in the presence of sulfuric acid results in a mixture of isomers from which the separation of 1-nitroanthraquinone is difficult and expensive.